Although Neisseria gonorrhoeae was established as an etiological agent of gonorrhea over ninety years ago, knowledge of its cell surface antigenic structure is far from complete. Studies on the isolation of antigenic fractions from the cell surface of gonococcus have been numerous but work has been predominantly directed toward serological classification. Since these fractions were fragments of lipopolysaccharides and outer membrane proteins obtained under denaturing conditions, no general agreement on their identity could be reached among different investigators.
Even though gonorrohea is one of the most prevalent infectious diseases in many countries, information is still lacking concerning the nature of the immune response of the host. It has been well established that in certain human diseases of bacterial etiology, the protective immune response is directed primarily toward antigens that are found only in the virulent forms. Since morphological studies of gonococcus have shown that Type 1 and 2 are virulent forms (Kellog et al., 1963; Kellog et al., 1968), these types have become the subject of further investigations in attempts to isolate a prophylactic immunogen.